Internal valves are used for a variety of commercial and industrial applications to control fluid flow between a fluid storage container and another container, hose, pipeline, etc. In particular, internal valves may protect against discharge of hazardous materials, compressed liquids, and gases such as, for example, propane, butane, and NH3 (anhydrous ammonia), when transferring such material between a first location and a second location. Internal valves employ flow control mechanisms that close in response to a sudden excess flow condition due to, for example, a broken, severed, or otherwise compromised flow path. Such flow control mechanisms are commonly referred to as poppet valves or excess flow valves, which are often used in applications requiring an automatic, safe cutoff of fluid flow in response to potential leaks or spills of potentially dangerous fluids.
The poppet valve typically operates based on a pressure differential across the internal valve. For example, the poppet valve opens when the inlet pressure is approximately equal to the outlet pressure. The internal valve will typically employ a bleed valve to equalize or balance the pressure across the flow control member before opening the main valve. In one example, an internal valve may be used on an inlet or an outlet of a large storage tank and keeps the tank from rupturing from excessive internal tank pressure. The bleed valve allows the tank to vent or bleed the pressurized gas through a bleed flow path and eventually through the poppet valve until the tank pressure drops to an acceptable level before fully opening the valve.